Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$157.87	3.497%	$163.3907	$163.39	$163.40	$163.40
Purchase #2	$82.44	8.685%	$89.5999	$89.60	$89.60	$89.60
Purchase #3	$40.37	3.783%	$41.8972	$41.90	$41.90	$41.90
Purchase #4	$192.88	10.311%	$212.7679	$212.77	$212.75	$212.80
Purchase #5	$75.91	3.346%	$78.4499	$78.45	$78.45	$78.40
Purchase #6	$211.46	5.830%	$223.7881	$223.79	$223.80	$223.80
Purchase #7	$250.65	5.575%	$264.6237	$264.62	$264.60	$264.60
7 purchase totals =	$1,011.58		$1,074.5174	$1,074.52	$1,074.50	$1,074.50